Friday, November 26, 2010

First of all, Happy Thanksgiving to my American blogger buddies. I hope you all had a wonderful day that included pie. Well, I guess anybody’s day could be wonderful and include pie, so the wish can be all-inclusive.

As mentioned in my previous post, we have known since birth that Daltrey is hearing impaired to some degree due to his extreme splashed white pattern (read about splashed white here, and look in the right column for links to all the color/pattern posts).

Not all foals with splashed white pattern are born deaf, but there’s a fairly high probability that they will be hearing impaired to some degree. Mating two affected horses will not necessarily produce an affected foal. Not all splashed white foals have blue eyes. It is inaccurate to attribute hearing impairment to the blue eye color; both traits are caused by splashed white in horses. Hearing impairment is caused by a lack of pigment in part of the inner ear.

Figuring out if your horse has a hearing problem and/or to what degree is not as easy as you might think. Like night blindness, some horses adapt better to it than others. Poco is night blind, but you'd never know it. Because Daltrey is so young, he’s still trying to figure out how his world works, and he has the double whammy of being both night blind and hearing impaired.

Some horses, like some people, are more reactive than others. One horse may spook at the slightest sound, while others seem to take everything in stride. Also like people, horses do not respond to every sound they hear. Although horses instinctively pay attention to the vocalizations of other equines, as well as sounds that are not part of their normal repertoire, they filter out much of what they hear. This helps them make sure that only relevant sounds are acted upon. We ignore most of the sounds around us even though we can certainly hear them. It’s this ability that allows us to filter out dozens of different conversations at a cocktail party and focus on only one.

I’m still learning what Daltrey can and can’t hear. I think that overall, his hearing is muffled or muted to some degree. For example, I have fed him in the run-in shed during rains and high winds, with acorns and stuff hitting the sides and roof. Sometimes he seems to acknowledge sounds, but isn’t startled or upset by them. What’s funny is when the other two bolt because of a noise, and he bolts because they do, though I know he has no idea why he’s running. I think the only sounds he perceives as sharp are percussive sounds like gunshots, car backfires, etc. I believe most of his impairment is in the mid-range. I know he can hear the sound of my voice when I call him, even if he’s in the back pasture. He can also hear things like the chain saw, weed whipper, electric saws, etc., that are higher pitched. He doesn’t react to a whisper or a soft voice inches from his head.

I’m not overly concerned about Daltrey’s hearing impairment. In fact, everything in my research pretty much brushed it off as being no big deal. Combined with his already laid-back temperament, it should be an asset for a trail horse. The biggest repercussions involve modifying training techniques. They can’t rely on voice cues, so must be trained using visual cues on the ground and tactile cues under saddle. The only other major consequence is learning to help your horse not be startled by the unseen and unexpected approach of people or other animals. But don’t most of us already do that, for safety’s sake?

You may have to warn others on the trail not to come up from behind him until you've turned him to face them. I suspect Bombay may have either hearing problems or daydreaming problems, because a lot of times he doesn't hear me coming, then startles once he sees me. I was walking him up a narrow trail last year and we stopped to rest. A couple of hikers came up from behind us and I told them it was okay to pass. Somehow, even with me talking to them, Bombay didn't know they were there. They had to squeeze beside him and the woman placed her hand on his shoulder. He threw his head up horrified, then instantly relaxed as soon as he realized it was just people. I had to apologize to the hikers for not realizing that my horse didn't know they were there.

Training deaf animals isn't more difficult, it just takes a bit o' figgerin'. Years ago my aging dogs lost their hearing, so I switched to visual commands for sit/down/stay. To call them, I would clap my hands, which they could see at a distance...except they learned not to look at me if they didn't want to "hear" what I was saying! Then I switched to stamping my foot to call them, which they could feel through their feet. (You might ask hikers on the trail to stamp, to let Daltry know that they are there...hungry predators don't stamp, so that will probably work for you).

Later in their long lives (both dogs lived to age 18+ years) they both went blind, so the visual cues were no good anymore...at that point, they were getting more than slightly senile, so I just kept them on a leash outside of the house.

Sounds like you are well informed about him and good to know all the things that might or might not be issues. He sounds like he will make an ideal trail horse (or competition if the crowd is muted it could be good!)

Lisa, the lack of pigment in the inner ear as a result of splashed white pattern prevents the growth of tiny hairs that are sound receptors. In the eyes, the lack of pigment causes the color but not sight impairment. Daltrey has so many patterns expressing themselves that it can be confusing. Basically, splashed white pattern is the cause of the blue eye color and the lack of pigment in the inner ears (and hearing impairment), BUT his night blindness is the result of his being homozygous LP/LP. Two different patterns.

From what I could tell, the term glass eyes is used interchangeably with other terms for blue eyes. They are no more prone to sight impairment or disease than any other color. However, because they often have pink eyelids, they can be prone to sun damage.

Daltrey's eyes are startling if you aren't used to Appy eyes with the white sclera.

daltrey, sweetie, i'm with you! my man and i have been suffering tinnitus latetly (permanentely?) and we visited an ear specialist yesterday and submitted to hearing tests, pressure tests, and all sorts of intrusive crap. now we're taking blood thinning meds three time a day, and magnesium. if they don't work, we'll have to have cortisone infusions (IV for an hour!). agh! we both cannot sleep at night because of the ringing. i wonder what is wrong with us. FYI, we are both very pale.

I was raised to avoid 'glass-eyed' horses...you know all of the old cowboy rumors and all, but never-the-less have ended up with several along the way. I have noticed that they do 'see' differently than brown-eyed horses. I have often wondered if if was more of a glare problem or perhaps a difference in depth perception?

The black horse that I have now has one full blue eye and one partial. I have often noticed that if he wants to see something out of the partial blue eye, he will often turn his head away as if to look out the brown part of his eye. It's very strange.